Boost pressure question

[Turbo6Smackdown]

I threw a turn and a half on the wastegate a few days ago to see what it would do. The car normally maxes out with a loose wastegate rod at 17 psi. Now it goes to 20 for a second and bleeds back off to about 17 again. Is that a boost leak or a wastegate malfunction.

 

[john keskes]

I think this is what's considered Boost creep.. slow reacting wastegate / waste gate hole needs to be opened up a bit ?

 

[Raeban]

Actually it is called boost overshoot and it is hard to say for certain the cause as several things affect the boost ramp rate. Are you trying to achieve a boost higher than 17 psi?

 

[Turbo6Smackdown]

I was hoping for an even twenty for reference. I have the factory boost solenoid still connected and using the chip. From what I've read it's better to do the boost by the chip, is that right? It's a more gradual onset of boost and it's consistent. What say you?

 

[Raeban]

Since you have a powerlogger check the log you are referring to and specifically look at boost pressure and report back what your wastegate DC% is. I have looked at too many logs recently to remember for sure which one was yours but I think your DC% was all in at 100% so if you want to reliably control boost with that setup you will need to make a hardware change. Either way, check to make sure.

As for what boost ramp I prefer, I prefer slow and low for the street to avoid blowing the tires off since I drive mine rain or shine, but prefer as fast as I can get it if the surface is good.

 

[Turbo6Smackdown]

I agree. And I will check that.

 

[butch2000]

I have the same issue , I am using the stock solenoid to control the waste gate , and get boost creep with my TE60 , is the a more accurate why to control the boost level ? I have considered some of the manual control valve's ,

 

[earlbrown]

The solution for boost creep depends on the original problem. If you have a wastegate rod pulled banjo tight to get the desired boost level, it can be caused by running out of throw at WOT. If the puck can only move 1/16" off the housing the flow can overwhelm the small curtain area.

In that case the fix it to get a wastegate that can make the desired boost pressure without using all the travel.


If the wastegate port can't flow the necessary amount of air to hold the boost level down, then it needs to be ported (or you have a turbo that's way to small).

 

[Raeban]

Just to be clear the OP has Boost Overshoot or Boost Spike if you prefer. Boost Creep is not the same thing as Boost Overshoot. Boost Overshoot is when your boost initially exceeds your desired level as the boost is building and ends when your boost levels out. It is caused by insufficient damping of your boost control system. Boost Creep is when your boost gradually rises after your desired boost level has been achieved and potentially rising until you run out of RPM or let off the throttle. This is caused by insufficient exhaust diversion around the exhaust turbine. Earl has given a common example above of what happens when we try to get the most out of an adjustable light duty wastegate.

 

[Turbo6Smackdown]

Yea. It's like my wastegate doesn't hold my boost pressure. Could I actually need a hd wastegate?

 

[Raeban]

Best answer is perhaps. Upgrading to a heavier spring in the actuator will allow you to run higher boost, but the amount of pressure signal is in the hands of your factory solenoid. Since you can't easily make changes to the factory solenoid DC% without changing chips with your setup the actuator will get you there. The alternative would be to get a manual boost controller like the RJC and try that. I would see the RJC as an investment for the future anyways. How much total boost do you anticipate running?

 

[Turbo6Smackdown]

Plan on running 25 or so. Don't wanna heat the air up too much. But I like how the solenoid gives me gradual boost, not all of it at one time. I won't have any traction then. I'm guessing a boost leak would or exhaust leak pre turbo could cause this too. What do you say.

 

[Raeban]

Exhaust or boost leaks could definitely cause low boost, gotta make sure they are fixed.